This invention relates to a woven 3D fabric and its method of production. In particular, the woven 3D fabric comprises multilayer warp yarns and two orthogonal sets of weft which interlace with the rows and the columns of the warp to provide a network-like structure to the fabric which may additionally incorporate between the rows and the columns of the interlacing warp multi-directionally orientated non-interlacing yarns to improve the fabric""s mechanical performance. Such a fabric is considered useful in technical applications like the manufacture of composite materials, filters, insulating materials, separator-cum-holder for certain materials, electrical/electronic items, protection material, etc.
In the conventional weaving process the foremost operation of shedding is limited in its design to form a shed in only the fabric-width direction. The employed warp, which is either in a single or a multiple layer, is separated into two parts in a xe2x80x98crossedxe2x80x99 manner, in the direction of the fabric-thickness through the employment of the heald wires which are reciprocated through their frames by means such as cams or dobby or jacquard to form a shed in the fabric-width direction. Each of these heald wires have only one eye located midway and all the employed heald assemblies are reciprocated in only the fabric-thickness direction to form a shed in the fabric-width direction. A weft inserted into this formed shed enables interconnection between the separated two layers of the warp. The so interconnected warp and weft results in an interlaced structure which is called the woven fabric. A fabric when produced using a single layer warp results in a sheet-like woven material and is referred to as a woven 2D fabric as its constituent yarns are supposed to be disposed in one plane. Similarly, when a fabric is produced using a multiple layer warp, the obtained fabric which is characteristically different in construction from the woven 2D fabric, is referred to as a woven 3D fabric because its constituting yarns are supposed to be disposed in a three mutually perpendicular plane relationship. However, in the production of both these types of woven 2D and 3D fabrics the conventional weaving process, due to its inherent working design, can only bringing about interlacement of two orthogonal sets of yarn: the warp and the weft. It cannot bring about interlacement of three orthogonal sets of yarns: a multiple layer warp and two orthogonal sets of weft. This is an inherent limitation of the existing weaving process. The present invention provides a dual-directional shedding method to form sheds in the columnwise and the row-wise directions of a multilayer warp to enable interlacement of the multilayer warp and two orthogonal sets of weft.
Certain technical fabric applications require complex or unusual shapes besides other specific characteristics for performance such as a high degree of fabric integration and proper orientation of the constituent yarns. For example, at present it is not possible to obtain a suitable fabric block from which preforms (reinforcement fabric for composite material application) of any desired shape may be cut obtained. This is because the present fabric manufacturing processes of weaving, knitting, braiding and certain nonwoven methods which are employed to produce preforms cannot deliver a suitable highly integrated fabric block from which preforms of any desired shape may be cut obtained. With a view to obtain certain regular cross-sectional shaped preforms, suitable fabric manufacturing methods working on the principles of weaving, knitting, braiding and certain nonwoven techniques have been developed. Such an approach of producing preforms having certain cross-sectional shapes is referred to as near-net shaping. However, through these various techniques preforms of only certain cross-sectional profiles can be produced and preforms of any desired shape cannot be manufactured. The obtaining of preforms of any desired shape can be made practically possible only if a highly integrated fabric block can be made available so that the required shape can be cut from it without the risk of its splitting up. Also, fabrics for other applications like filters of unusual shapes can be similarly cut obtained from a suitable fabric block. For analogy, this strategy of obtaining any desired shape of three-dimensional fabric item may be seen as the cutting of different shapes of fabric items from a suitable sheet of 2D fabric, for example, during the manufacture of a garment. Therefore, as can be inferred now, to cut obtain three-dimensional fabric items of any desired shape it is essential to first produce a highly integrated fabric in the form of a block. The present invention provides a novel method to interlace a multilayer warp and two orthogonal sets of weft to produce a thoroughly interlaced woven 3D fabric construction which may additionally incorporate non-interlaced, multi-directionally orientated yarns to impart mechanical performance to the fabric, as shown in FIG. 1, to be useful in technical applications.
An objective of this invention is to make available a block of network-like, highly integrated 3D fabric which may additionally incorporate non-interlaced multi-directionally orientated yarns to impart proper mechanical strength to the fabric so that suitable fabric items of any desired shape for use in technical applications can be cut without the risk of its splitting up. Because certain fabric items may be obtained easily this way, such an approach can be advantageous in the manufacture of preforms, i.e. reinforcement fabric for composites application, filters etc. of any desired shape.
Another objective of this invention is to provide a dual-directional shedding method to enable interlacement of three orthogonal sets of yarn: a set of multilayer warp and two orthogonal sets of weft. Such an interlacement of the three orthogonal sets of yarn is necessary to provide a high degree of integrity to the fabric to render the fabric resistant to splitting up in the fabric-width as well as in the fabric-thickness directions. This way the objective of producing a network-like interlaced 3D fabric, which may additionally incorporate non-interlacing, multi-directionally orientated yarns, is made possible.
The integrity of the fabric is achieved through the formation of multiple row-wise and columnwise sheds in the employed multiple layer warp. Two orthogonal sets of weft when inserted in the formed row-wise and columnwise sheds produce a network-like, interlaced 3D fabric. Because the foremost operation of the weaving process happens to be the shedding operation, all other subsequent complementing operations of the weaving process, for example picking, beating-up etc., will follow suit accordingly. As this invention concerns the method of enabling interlacement of two orthogonal sets of weft and a multilayer warp by way of forming sheds in the columnwise and row-wise directions of the multilayer warp and to additionally incorporate multi-directionally orientated non-interlacing yarns in different directions of the fabric to produce a highly integrated fabric structure having a high mechanical performance, it will be described in detail. The subsequent complementing weaving operations like picking, beating-up, taking-up, letting off etc. will not be described as these are not the objectives of this invention. With a view to keep the description simple and to the point, the simplest mode of carrying out the dual-directional shedding operation will be exemplified and will pertain to the production of the woven plain weave 3D fabric only. The method of producing numerous other weave patterns through this invention will be apparent to those skilled in the art and therefore it will be only briefly mentioned as these various weave patterns can be produced on similar lines without deviating from the spirit of this invention.